High speed chop tank slapping

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3/14/2018 4:44 AM

I can’t for the life of me get this bar swapping sensation to go away when I’m on a rough track at high speeds. It’s sprung and valved for my weight and riding ability, 17 fc350 kyb a kit front forks, bladder conversion on the rear with pro circuit linkage. I was at englishtown the other week and got her dialed in pretty well but then I go to field of dreams which seemed to have a harder base so the chop is more violent when it comes to bar banging. What do you guys suggest? I tried Comp/rebound settings but eventually got lost. Thanks for any and all help. Oh and maybe it’s me and my short stature bc my 15 yz250f and 14 crf250r did the same stuff at high speeds with fc tunes suspension

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3/14/2018 5:52 AM
Edited Date/Time: 3/14/2018 5:52 AM

Lower the fork legs in the triple clamps about 5mm or add about 5mm sag in the rear.

Paw Paw

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3/14/2018 6:45 AM

Unfortunately the forks are about as low as they can go, I had the sag at 110 but the front end didn’t seem to like that very much so I went to 106. At 110 the forks were very harsh feeling in rough sections

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3/14/2018 6:55 AM

Is your stem nut tight or are the bearings worn out? I had the same issue on my kx450. Replaced the bearings and torqued the nut and its all good. Best sign is bars flopping to one side on the stand.

Also you might be hanging over the front of the bike too much.

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3/14/2018 7:25 AM

Bike has around 30 hours on it don’t think the bearings are bad just yet, pretty sure I torqued everything when I installed the triples but I’ll check again. Too far forward can cause head shake? I figured more weight up front would lessen it

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3/14/2018 7:54 AM

Add a bit of air pressure, try and get the forks a bit higher in the stroke.

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Tomac and/or Anderson for 2020.....

3/14/2018 8:08 AM

Kyb spring forks. But yes I did go up a few click on compression and it helped but then would push a little more in the turns. Maybe I’m just asking for to much out of these a kit forks

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3/14/2018 8:45 AM

Try to speed up the rebound in the forks.

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3/14/2018 8:52 AM

ben5020 wrote:

Bike has around 30 hours on it don’t think the bearings are bad just yet, pretty sure I torqued everything when I installed ...more

If you lean forward you compress the forks thus lowering the front of the bike. Leaning back lowers the rear and gives more stability and less headshake.

Amount of hours is irrelevant sometimes. We have all seen brand new bikes and cars break. Still something to look at just to be sure. Especially if you had it apart.

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3/14/2018 11:44 AM

Seems like you've covered most of your bases, but I suggest tightening the head nut so the bars don't flop on their own weight- (also stated above) but to emphasize, you definitely want some resistance on the turning. Also, roll the bars back a tad and squeeze the bike with your knees. Maybe drag the rear brake, depending on the situation.

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3/14/2018 11:49 AM

ra450 wrote:

Try to speed up the rebound in the forks.

Agreed. ^^

I remember MXA always saying if your forks are too soft, you will get headshake and they suggested going to stiffer springs. Obviously, the front end would drop, steepening the rake. I imagine the stiffer springs help speeding up the rebound too. The forks could be packing and not contacting the ground on throttle chop. A quality slow-mo video of you riding the bike could help determine if this is happening.

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3/14/2018 12:15 PM

Are you accelerating, decelerating or maintaining speed?

Some other things to check:
Front wheel bearing excess play?
Is the front wheel true?
Front tire seated properly?

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3/14/2018 2:21 PM

Same problem same tracks you ride. 14 Crf250r and 17 Crf450r. I’ve tried all the common suggestions and nothing works. I blame myself. I’ve been told by a local suspension guy that my suspension is to soft but haven’t had it done yet.

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3/14/2018 3:18 PM

Turn the comp clickers on forks all in, and see if the headshake issue gets any improvement. That's a way to troubleshoot your valving.

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Livin' the dream, two wheels at a time!

3/14/2018 3:19 PM

Naanak wrote:

Same problem same tracks you ride. 14 Crf250r and 17 Crf450r. I’ve tried all the common suggestions and nothing works. I blame ...more

I was under the assumption that too stiff of suspension will cause headshake, wonder which one is true? Stiff or soft is to blame.

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3/14/2018 3:21 PM

easydoesit wrote:

Are you accelerating, decelerating or maintaining speed?

Some other things to check:
Front wheel bearing excess play?
Is the ...more

It’s when I’m accelerating and once it gets violent I let off. Think I’m 4th gear almost pinned. Wheel and tire are good

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3/14/2018 4:54 PM

Go in on hc nut 1/4 and see if any improvement.

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Livin' the dream, two wheels at a time!

3/14/2018 4:55 PM

ben5020 wrote:

I was under the assumption that too stiff of suspension will cause headshake, wonder which one is true? Stiff or soft is to ...more

When I called FC about the issue they had me go softer on the clickers (did not help). The local guy said I needed to go up a spring rate and much stiffer valving. So I honestly have no idea.

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3/14/2018 10:41 PM

Rear spring too stiff? Maybe the pc link makes it stiffer on the initial stroke and rear isn't settling...???

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3/15/2018 4:03 AM

RyanLester761 wrote:

Rear spring too stiff? Maybe the pc link makes it stiffer on the initial stroke and rear isn't settling...???

My sag numbers are fine so I don’t think it’s a rear spring/shock issue. Maybe I’m just too far forward and it’s getting all whacked out bc of it?

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3/15/2018 6:09 AM

My RMZ450 always gets headshake with high speed throttle chop if fork rebound is too slow. Never have any trouble now l have less offset triple clamps.

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Melbourne, Australia. Current rides: '11 RMZ450, '84 CR500, '06 DRZ400, '79 KX250 with 400 engine, '06 GSXR1000 full Yosh racebike.

3/15/2018 6:10 AM

RyanLester761 wrote:

Rear spring too stiff? Maybe the pc link makes it stiffer on the initial stroke and rear isn't settling...???

ben5020 wrote:

My sag numbers are fine so I don’t think it’s a rear spring/shock issue. Maybe I’m just too far forward and it’s getting all ...more

Thats what i told you fam. Ass over the fender over chop. Look at the pros

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3/15/2018 1:39 PM

I’m running a 17 FX450, and I’ve found that anything less than 107mm of sag will make the front end very unstable. As a matter of fact, yesterday I decided to try 105 and ended up with the same problem as you over the whoops. Went to 108mm, problem solved.

As others have mentioned, too slow of rebound on the forks can do it also.

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3/15/2018 3:01 PM

Naanak wrote:

Same problem same tracks you ride. 14 Crf250r and 17 Crf450r. I’ve tried all the common suggestions and nothing works. I blame ...more

ben5020 wrote:

I was under the assumption that too stiff of suspension will cause headshake, wonder which one is true? Stiff or soft is to ...more

I've seen it happen from both scenarios. Tried to explain that to a buddy after his suspension tuner left the rear alone and went up on the fork spring rate. He couldn't figure it out. Finally had a more well known tuner look at them and he backed up everything I said.

I have also seen it happen when the front is too soft and riding too low in the stroke. Suspension in an interesting topic and I love learning about it.

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

3/15/2018 4:37 PM

get stronger arms maybe?

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3/16/2018 4:04 AM
Edited Date/Time: 3/16/2018 4:05 AM

Radfonz wrote:

get stronger arms maybe?

Hahahahaha I’ll be sure to eat my spinach and see if it helps

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3/16/2018 4:18 AM

My '14 250SX had severe headshake in decel chop, to the point that it would nearly rip the bars from your hands. I don't claim to know a lot about setup and tried numerous solutions from "experts" to no avail. I now have a '16 FC350 that came with a Ride Engineering stabilizer. I know that it's a band-aid for shitty setup but I've yet to feel the bars twitch under any circumstances. I highly recommend it if all else fails and you're tired of chasing your tail.

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3/16/2018 6:47 AM

I had a '17 TC 250 with AER forks, no headshake what so ever...

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3/16/2018 8:46 AM

slipdog wrote:

I had a '17 TC 250 with AER forks, no headshake what so ever...

But you also know a lot about suspension and how to set it up properly whistling

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

3/16/2018 8:49 AM

slipdog wrote:

I had a '17 TC 250 with AER forks, no headshake what so ever...

You didn't get the memo air forks are no good?

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